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Approach Distance (approach + distance)
Selected AbstractsPredator Inspection Behaviour in a Characin Fish: an Interaction between Chemical and Visual Information?ETHOLOGY, Issue 9 2003Grant E. Brown Recent evidence suggests that predator inspection behaviour by Ostariophysan prey fishes is regulated by both the chemical and visual cues of potential predators. In laboratory trials, we assessed the relative importance of chemical and visual information during inspection visits by varying both ambient light (visual cues) and predator odour (chemical cues) in a 2 × 2 experimental design. Shoals of glowlight tetras (Hemigrammus erythrozonus) were exposed to a live convict cichlid (Archocentrus nigrofasciatus) predator under low (3 lux) or high (50 lux) light levels and in the presence of the odour of a cichild fed tetras (with an alarm cue) or swordtails (Xiphophorus helleri, with an alarm cue not recognized by tetras). Tetras exhibited threat-sensitive inspection behaviour (increased latency to inspect, reduced frequency of inspection, smaller inspecting group sizes and increased minimum approach distance) towards a predator paired with a tetra-fed diet cue, regardless of light levels. Similar threat-sensitive inspection patterns were observed towards cichlids paired with a swordtail-fed diet cue only under high light conditions. Our data suggest that chemical cues in the form of prey alarm cues in the diet of the predator, are the primary source of information regarding local predation risk during inspection behaviour, and that visual cues are used when chemical information is unavailable or ambiguous. [source] Ultrahigh-resolution structure of high-potential iron,sulfur protein from Thermochromatium tepidumACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2002Lijun Liu Crystals of the high-potential iron,sulfur protein (HiPIP) from Thermochromatium tepidum diffract X-rays to 0.80,Å using synchrotron radiation at 100,K. The crystal structure of this HiPIP was refined at this ultrahigh resolution with anisotropic temperature factors for all atoms to conventional crystallographic R factors of 0.092 and 0.101 for Fo > 4,(Fo) and all reflections, respectively. The present structure provides a more precise picture than the previous 1.5,Å structure and allows location of the positions of most H atoms. The structure revealed a partly hydrophobic cavity near the main hydrophobic area and a much larger inter-cluster approach distance (23.454,Å, the c constant of the unit cell) in the crystal packing than other types of HiPIPs. The structural features involved in the electron-transfer reaction of HiPIP are discussed. [source] Morphological correlates of burst speed and field movement patterns: the behavioural adjustment of locomotion in wall lizards (Podarcis muralis)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2003FLORENTINO BRAÑA Locomotion of lizards has clear morphological determinants and is important for developing activities such as feeding, social interaction and predator avoidance. Thus, morphological variation is believed to have fitness consequences through affecting locomotor performance. This paper firstly evaluates the dependence of burst speed on morphology, and secondly examines the movement patterns of free-ranging undisturbed wall lizards (Podarcis muralis) engaged in several kinds of activity. Body size was the most important correlate of burst speed as performed at the optimal temperature for running in the laboratory. After removing size effects from performance and morphological traits, the length of some particular limb segments had positive influence on burst speed, but these effects were weak, each trait explaining less than 16% of variance in burst speed. Free-ranging P. muralis exhibited intermittent locomotion, with movement sequences interrupted by frequent short pauses. Field movement patterns greatly differed depending upon the kind of activity and were in most aspects independent of the size and sex of the animal. P. muralis involved in thermoregulation performed short and low-speed displacements; exploratory activities were characterized by frequent, slow and short movements. On the contrary, lizards involved in intraspecific pursuits and predator escape developed comparatively high speeds, although only exceptionally did they attain the size-specific burst speed predicted from the laboratory trials. Speed of escape increased with distance to the refuge and the animals are able to assess predation risks to modulate approach distance, speed and pauses, so maximum exertion is seldom required. The evolution of locomotor capacities exceeding routine needs is discussed in the context of the principle of ,excessive construction'. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80, 135,146. [source] Electrosensory avoidance of metal obstacles by the paddlefishJOURNAL OF FISH BIOLOGY, Issue 2 2000C. Gurgens Paddlefish Polyodon spathula detected and avoided obstacles with an exposed metallic surface but not plastic objects. An aluminium obstacle was avoided from significantly greater minimum approach distances than were any of the other obstacles. No significant difference was detected between the plastic and plastic-covered aluminium obstacles, while control values were significantly less than for all obstacle types. Avoidance distances measured at different water conductivities were not significantly different. Fish collided frequently with the plastic and plastic-covered aluminium obstacles, and with the control site, suggesting that these obstacles were not detected by the electrosensory apparatus. The aluminium obstacle was avoided successfully in all test runs. The unambiguous avoidance behaviour elicited by the aluminium obstacle suggests that large metallic structures, such as locks and dams, have the potential to interfere with paddlefish migrations. ©2000 The Fisheries Society of the British Isles [source] | ||||||||||